1. Field of the Invention
The present invention relates to a novel substituted thiophene derivative and a plant disease control agent comprising the same as an active ingredient.
2. Description of the Related Art
The plant disease control agent which has been developed in recent years and has a selective activity differs from a conventionally used, nonselective plant disease control agent, and can exhibit steady effect at a low dosage. However, the new control agent has a problem of developing a resistant strain in repeated use and leading to reduction in efficacy.
For example, a benzimidazole-based fungicide has a wide fungicidal spectrum and also exhibits an excellent effect on Botrytis cinerea. However, such fungicide caused in 1970's a drastic reduction in efficacy due to appearance of a resistant fungus. A dicarboxyimide-based fungicide was focused attention as a replacement of the benzimidazole-based fungicide. Nevertheless a resistant fingus also appeared in the 1980's also against the dicarboxyimide-based fungicide. Consequently, the countermeasure for controlling the resistant Botryrtis cinerea has become a serious problem in the world.
On the other hand, an azole-based fungicide has a wide fungicidal spectrum and is an excellent pesticide which exhibits efficacy at a hitherto unexampledly low dosage particularly for powdery mildew and rust of various crops and also for scab of apple and pear. However, a resistant fungus against this pesticide has recently appeared and also led to a sharp reduction in the pesticide efficacy. The repeated use of the pesticide also tends to be restricted.
Thus, the appearance of the pesticide resistant fungus has become an inevitable problem for the selective plant disease control agent, and accordingly development of a new pesticide is now an urgent subject.
Many aromatic carboxylic acid anilide derivatives have been conventionally known to exert fungicidal activity. Recently, for example, Japanese Laid-Open Patent HEI 5-221994 and 6-199803 (European Patent A-545099 and A-58930 1) have described that various carboxylic acid anilide derivatives exhibit effect on Botrytis cinerea.
On the other hand, European Patent A-737682 has described fungicidal activity of a substituted thiophene derivative represented by the general formula: ##STR2## wherein Q is a hydrogen, fluorine, chlorine, bromine or iodine atom, or a methyl, trifluoromethyl, methoxy, methylthio, methylsulfoxy, methylsulfonyl, cyano, acetyl, nitro, alkoxycarbonyl or amino group; R is a straight or branched alkyl group having 1-12 carbon atoms, straight or branched halogenoalkyl group having 1-12 carbon atoms, straight or branched alkenyl group having 2-10 carbon atoms, straight or branched halogenoalkenyl group having 2-10 carbon atoms, alkylthioalkyl group having 2-10 carbon atoms, alkyloxyalkyl group having 2-10 carbon atoms, cycloalkyl group having 3-10 carbon atoms, halogenocycloalkyl group having 3-10 carbon atoms, or phenyl group having 1-3 substituents; substituent of phenyl group is a hydrogen or halogen atom or an alkyl group having 1-4 carbon atoms, alkenyl group having 2-4 carbon atoms, alkynyl group having 2-4 carbon atoms, cycloalkyl group having 3-6 carbon atoms, alkoxy group having 1-4 carbon atoms, halogenoalkoxy group having 1-4 carbon atoms, alkylthio group having 1-4 carbon atoms, alkylsulfoxy group having 1-4 carbon atoms, alkylsulfonyl group having 1-4 carbon atoms, cyano group, acyl group having 2-4 carbon atoms, alkoxycarbonyl group having 2-4 carbon atoms, amino or amino group substituted with alkyl group having 1-3 carbon atoms; R and --NHCOAr are adjacent to each other; and Ar is a group represented by the general formulas (B1l)-(B8); ##STR3## wherein R.sup.1 is a chlorine, bromine or iodine atom, or a methyl, ethyl, difluoromethyl or tifluoromethyl group; R.sup.2 is a hydrogen atom, or a methyl, trilluormethyl or amino group; and n is an integer of 0-2.
The present inventors have considered that the application field will be extended with a small lead on the environment if a pesticide having higher control activity and extended residual effect for a long period can be developed.
Consequently the object of the invention is to save labor and enhance safety for the environment by providing a plant disease control agent having a wide fungicidal spectrum and long residual effect.